This invention relates to a bearing assembly for a shaft journal and more particularly to a bearing assembly that is less likely to produce fretting along the surface of a journal.
The Timken Company manufactures and sells, under the trademark AP, a self-contained, prelubricated, preset and sealed bearing assembly for use at the ends of axles and other shafts. This highly versatile bearing assembly has found widespread use on the journals at the ends of rail car axles, in that it fits easily over these journals and mates with a housing in a truck side frame. It basically consists of a two-row tapered roller bearing, seals fitted to each of the ends of the bearing cup, wear rings inside the seals and against the ends of the bearing cones, and a backing ring at the end of the inboard wear ring. Once the journal of the shaft is machined to a prescribed diameter and provided with a fillet of appropriate contour, the bearing assembly is simply passed over the journal and clamped between the fillet and an end cap with bolts that thread into the end of the journal and turn down against the end cap. U.S. Pat. No. 3,494,682 shows a typical AP bearing assembly fitted over an axle journal and clamped in place with an end cap and bolts.
The wear ring, which the seals embrace to close the ends of the bearing, fit snugly around the journal. Indeed, interference fits exist between the two wear rings and the journal, and consequently they must be pressed onto the journal. In use, a minute amount of movement occurs between the snugly fitted wear rings and the journal, owing to flexure in the axle or shaft, and this movement is most pronounced at the inboard wear ring. The movement produces fretting which in time imparts a groove to the journal and an enlargement of the ring bore. As a consequence, the inboard wear ring works loose and does not remain concentric with respect to the surrounding seal.
The present invention resides in a bearing assembly for use on a journal at the end of an axle or other shaft, and the end of the bearing for this bearing assembly is closed with a seal which bears against a seal ring or sleeve. That ring or sleeve is larger than the shaft, so a slight clearance exists between it and the shaft. The seal ring or sleeve finds its center from a backing ring, which also forms part of the bearing assembly and fits snugly against a shoulder or fillet on the shaft.